| 1. |
- Felicetti, Leonard, et al.
(författare)
-
A comparison among classical and SDRE techniques in formation flying orbital control
- 2013
-
Ingår i: 2013 IEEE Aerospace Conference. - Piscataway, NJ : IEEE Communications Society. - 9781467318112
-
Konferensbidrag (refereegranskat)abstract
- A key point in formation flying mission design is represented by the accuracy and the cost of maintaining the requested orbital configuration. In fact, the relative geometry among spacecraft should be kept within tight limits in order to accomplish payload missions. At the same time, this effort requires to accommodate onboard the relevant amount of propellant, which should be correctly evaluated. The quest for optimal control strategy faces the non linear nature of the orbital dynamics, furthermore affected by perturbations that can be only modeled and therefore not perfectly known. As a result, traditional optimal strategies as the Linear Quadratic Controller (LQR), which design can be achieved under the hypothesis of simplified (as an example linearized) dynamics, not always meet the objective. Innovative approaches, like the State Dependent Riccati Equation (SDRE) technique, allow to better take into account, at an increasing level of approximations, the real dynamics. The paper presents extensive results of the simulations carried out for two different problems in formation flying control: the maintaining of a desired relative geometry and the acquisition of a requested configuration. A relevant point, also with respect to currently available literature, is the fact that the considered reference orbits have an eccentricity different from zero
|
|
| 2. |
- Felicetti, Leonard, et al.
(författare)
-
A multi-spacecraft formation approach to space debris surveillance
- 2016
-
Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 127, s. 491-504
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a new mission concept devoted to the identification and tracking of space debris through observations made by multiple spacecraft. Specifically, a formation of spacecraft has been designed taking into account the characteristics and requirements of the utilized optical sensors as well as the constraints imposed by sun illumination and visibility conditions. The debris observations are then shared among the team of spacecraft, and processed onboard of a “hosting leader” to estimate the debris motion by means of Kalman filtering techniques. The primary contribution of this paper resides on the application of a distributed coordination architecture, which provides an autonomous and robust ability to dynamically form spacecraft teams once the target has been detected, and to dynamically build a processing network for the orbit determination of space debris. The team performance, in terms of accuracy, readiness and number of the detected objects, is discussed through numerical simulations.
|
|
| 3. |
- Felicetti, Leonard, et al.
(författare)
-
Adaptive thrust vector control during on-orbit servicing
- 2014
-
Ingår i: AIAA SPACE 2014 Conference and Exposition. - : American Institute of Aeronautics and Astronautics, AIAA. - 9781624102578
-
Konferensbidrag (refereegranskat)abstract
- On-orbit servicing missions often include a final propulsive phase where a spacecraft pushes the other one towards a different orbit. Specifically this is the case of the debris grasping mission where the chaser, after capturing the target by means of robotic arms, has to perform a de-orbit operation. The large thrust involved needs a perfect alignment with respect to the center of mass or the system composed by chaser and target, in order to avoid attitude changes. Such accurate alignment is quite difficult to achieve especially when the characteristics of the target are not perfectly known. A procedure is proposed in this paper, allowing a complete estimation of the center of mass position and of the moments of inertia of the system, starting from the data obtained by the gyros mounted on board of the spacecraft. The output is used to design a maneuver for correcting the target and chaser relative position by moving the robotic arms. Numerical simulations show the proficiency and the applicability of the estimation algorithm and of re-alignment maneuver to a selected mission scenario.
|
|
| 4. |
- Felicetti, Leonard, et al.
(författare)
-
Analytical and numerical investigations on spacecraft formation control by using electrostatic forces
- 2016
-
Ingår i: Acta Astronautica. - : Elsevier BV. - 0094-5765 .- 1879-2030. ; 123, s. 455-469
-
Tidskriftsartikel (refereegranskat)abstract
- The paper investigates some analytical and numerical aspects of the formation control exploited by means of inter-spacecraft electrostatic actions. The analysis is based on the evaluation and check of the stability issues by using a sequence of purposely defined Lyapunov functions. The same Lyapunov approach can also define a specific under-actuate control strategy for controlling selected “virtual links” of the formation. Two different selection criteria for these links are then discussed, showing the implications on the control chain. An optimal charge distribution strategy, which assigns univocally the charges to all the spacecraft starting from the charge products computed by the control, is also presented and discussed. Numerical simulations prove the suitability of the proposed approach to a formation of 4 satellites.
|
|
| 5. |
- Felicetti, Leonard, 1982-, et al.
(författare)
-
Attitude and Orbital Dynamics of a Variable-Geometry, Spinning Solar Sail in Earth Orbit
- 2017
-
Konferensbidrag (refereegranskat)abstract
- At the ISSS 2013, a novel concept of variable-geometry solar sail was introduced: deployed in the shape of a three-dimensional quasi-rhombic pyramid (QRP), the sail exploited its shape and shift between center of mass and center of pressure to naturally achieve heliostability (stable sun-pointing) throughout the mission. In addition, mechanisms allowed to vary the flare angle of the four booms in opposite pairs, thus allowing to control the area exposed to the sun without the need of slew maneuvers. Using these adjustments in favorable orbital positions, it is possible to build a regular pattern of acceleration to achieve orbit raising or lowering without the need of propulsion system or attitude control. Subsequent more detailed investigations revealed that eclipses, even if lasting only a fraction of the orbit, have a substantial (and negative) impact on the heliostability effect: and even a small residual angular velocity, or disturbance torque, are enough to cause the spacecraft to tumble. In this work, we present a novel and improved concept which allows the sail to preserve its attitude not only with eclipses, but also in presence of disturbance torques such as the gravity gradient. The solution we propose is to add a moderate spin to the solar sail, combined with ring dampers. The gyroscopic stiffness due to the spin guarantees stability during the transient periods of the eclipses, while the heliostability effect, combined with the dampers, cancels any residual unwanted oscillation during the parts of the orbit exposed to the sun, and at the same time guarantees continuous sun-pointing as the apparent direction of the sun rotates throughout the year. Both theoretical and numerical analyses are performed. First, stability bounds on the sail design are calculated, obtaining conditions on the flare angles of the sail, in the different orbital regimes, to test the robustness of the concept. Then, a numerical analysis is performed to validate the study in a simulated scenario where all perturbations are considered, over extended amount of time. The concept targets equatorial orbits above approximately 5,000 km. Results show that an increase of 2,200 km per year for a small device at GEO can be achieved with a CubeSat-sized sail.
|
|
| 6. |
- Felicetti, Leonard, et al.
(författare)
-
Attitude Coordination of Multiple Spacecraft for Space Debris Surveillance
- 2017
-
Ingår i: Advances in Space Research. - : Elsevier. - 0273-1177 .- 1879-1948. ; 59:5, s. 1270-1288
-
Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the attitude coordination of a formation of multiple spacecraft for space debris surveillance. Off-the-shelf optical sensors and reaction wheels, with limited field of view and control torque, respectively, are considered to be used onboard the spacecraft for performing the required attitude maneuvers to detect and track space debris. The sequence of attitude commands are planned by a proposed algorithm, which allows for a dynamic team formation, as well as performing suitable maneuvers to eventually point towards the same debris. A control scheme based on the nonlinear state dependent Riccati equation is designed and applied to the space debris surveillance mission scenario, and its performance is compared with those of the classic linear quadratic regulator and quaternion feedback proportional derivative controllers. The viability and performance of the coordination algorithm and the controllers are validated through numerical simulations.
|
|
| 7. |
- Felicetti, Leonard, et al.
(författare)
-
Attitude coordination strategies in satellite constellations and formation flying
- 2015
-
Ingår i: 2015 IEEE Aerospace Conference. - Piscataway, NJ : IEEE Communications Society. - 9781479953790
-
Konferensbidrag (refereegranskat)abstract
- The coordination of the attitude among different spacecraft belonging to a multiple platform system (formation or constellation) is a basic requirement in several missions, mainly the ones involving sensors like radars or optical interferometers. It is also an open topic in research, above all as it matches the characteristics of the current trend towards interoperability and federated systems. Different approaches are possible to define and chase such a coordinated attitude. The classic control strategy is the socalled leader-follower architecture, where all spacecraft depend on ("follow") the behavior of a single master. Alternatively, the behavioral approach involves a continuous re-selection of the desired target configuration which is computed on the basis of the behavior of all the platforms. A third possibility is to define a "virtual" architecture, especially suitable with respect to the mission requirements, which is not dependent on the current kinematic state of the platforms. The paper proposes a unified treatment of these concepts by using some fundamental definitions of the consensus dynamics and cooperative control. The convergence to the targeted configuration is addressed both analytically, by using Lyapunov stability criteria, and numerically, by means of numerical simulations. The attitude requirements and constraints are highlighted and a solution for the control algorithm - involving continuous actuators on each platform - is developed. A comparative analysis of different optimal control strategies, the Linear Quadratic Regulation (LQR) and the State Dependent Riccati Equation (SDRE) - suitably modified to address the needs of coordination - is presented. The results show the general value of the proposed approach with respect to either linear or nonlinear models of the dynamics.
|
|
| 8. |
- Felicetti, Leonard, 1982-, et al.
(författare)
-
Attitude Stability and Altitude Control of a Variable-Geometry Earth-Orbiting Solar Sail
- 2016
-
Ingår i: Journal of Guidance Control and Dynamics. - 0731-5090 .- 1533-3884. ; 39:9, s. 2112-2126
-
Tidskriftsartikel (refereegranskat)abstract
- A variable-geometry solar sail for on-orbit altitude control is investigated. It is shown that, by adjusting the effective area of the sail at favorable times, it is possible to influence the length of the semimajor axis over an extended period of time. This solution can be implemented by adopting a spinning quasi-rhombic pyramidal solar sail that provides the heliostability needed to maintain a passive sun-pointing attitude and the freedom to modify the shape of the sail at any time. In particular, this paper investigates the variable-geometry concept through both theoretical and numerical analyses. Stability bounds on the sail design are calculated by means of a first-order analysis, producing conditions on the opening angles of the sail, while gravity gradient torques and solar eclipses are introduced to test the robustness of the concept. The concept targets equatorial orbits above approximately 5000km. Numerical results characterize the expected performance, leading to (for example) an increase of 2200km/yr for a small device at geostationary Earth orbit.
|
|
| 9. |
- Felicetti, Leonard, et al.
(författare)
-
Coordinated attitude control for enhanced shape stability of a space web
- 2011
-
Ingår i: 62nd International Astronautical Congress 2011 : (IAC 2011). - Paris : International Astronautical Federation. - 9781618398055 ; , s. 8127-8134
-
Konferensbidrag (refereegranskat)abstract
- Large, reconfigurable and light orbiting structures are necessary to accomplish a number of tasks, such as the ones related to astronomy and fundamental physics missions, where very large telescope or other sensor arrays are needed. Given the technical limits imposed to the mass at launch, a mostly studied solution can be found in the formation of many satellites controlled in such a way that they can be considered as a virtual structure. This is possible only if synchronized and very accurate control is accomplished. The present paper focuses on the alternative solution represented by the space webs, intended as a set of small corner satellites connected by tethers: along the ropes of the web small robotic systems can move like spiders to position and re-locate, at will, pieces of hardware devoted to specific missions. In this sense, this work is the natural prosecution of previous studies of the same authors, where the advantages, drawbacks and possible solutions have been analyzed. In fact, the presence of rigid links would add the advantage of a simpler control strategy to the typical benefits of formation flying. Unfortunately, there is no stable configuration for an orbiting two dimensional web made by light, flexible tethers, since it cannot support compression forces caused by the gravity gradient. However, if the net is initially rotating (at a sufficiently high velocity) in the orbital plane, the centrifugal force counteracting the gravity gradient compression leads to a stable motion. Residual shape deformations are still present: in order to increase the desired shape stability of the web, it is possible to introduce a coordinated attitude control of the corner satellites, as an example by means of reaction wheels. This paper shows some preliminary results on the dynamics of tethers which are subjected to a torque at their tip. The analysis requires to add to previous models the attitude of the corner spacecraft as well as of the section the tethers are divided in. At this step, tethers are modeled as axial springs with no compression resistance. The paper, based on a performing code specifically written, reports the results for a number of simulations in order to provide helpful insight in this unusual dynamics
|
|
| 10. |
- Felicetti, Leonard, et al.
(författare)
-
Coordinated attitude control for multiple heterogeneous satellites missions
- 2012
-
Ingår i: AIAA/AAS Astrodynamics Specialist Conference 2012. - Reston, VA : American Institute of Aeronautics and Astronautics, AIAA. - 9781624101823
-
Konferensbidrag (refereegranskat)abstract
- The paper investigates cooperative control strategies for spacecraft formations, also in case platforms are not homogeneous but differs in attitude control actuators. Specifically, either a common inertial or a time-varying pointing are considered as requirements for a formation of spacecraft, controlled either entirely by reaction wheels or partly by wheels and partly by thrusters. Two control strategies, namely the classical leader-follower or a more cooperative one, also labelled as behavioural based, where the kinematic state of each spacecraft is known to the others and enters in their command loop, are applied. In order to actually compute the actions, two controllers are considered: a classical proportionalderivative (PD) and an optimal one using the variable gain state dependent Riccati equation (SDRE). Numerical simulations to validate the approach are presented and, within this implementation, SDRE approach shows to succeed even in cases when PD fails
|
|
| 11. |
|
|
| 12. |
- Felicetti, Leonard, et al.
(författare)
-
Drag balance Cubesat attitude motion effects on in-situ thermosphere density measurements
- 2014
-
Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 54:3, s. 489-498
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamics of Cubesats carrying a drag balance instrument (DBI) for in situ atmosphere density measurements is analyzed. Atmospheric drag force is measured by the displacement of two light plates exposed to the incoming particle flow. This system is well suited for a distributed sensor network in orbit, to get simultaneous in situ local (non orbit averaged) measurements in multiple positions and orbit heights, contributing to the development and validation of global atmosphere models. The implementation of the DBI leads to orbit normal pointing spinning two body system. The use of a spin-magnetic attitude control system is suggested, based only on magnetometer readings, contributing to making the system simple, inexpensive, and reliable. It is shown, by an averaging technique, that this system provides for orbit normal spin axis pointing. The effect of the coupling between the attitude dynamics and the DBI is evaluated, analyzing its frequency content and showing that no frequency components arise, affecting the DBI performance. The analysis is confirmed by Monte Carlo numerical simulation results
|
|
| 13. |
- Felicetti, Leonard, et al.
(författare)
-
Evaluation of control strategies for spacecraft electrostatic formation keeping
- 2014
-
Ingår i: 2014 IEEE Aerospace Conference. - Piscataway, NJ : IEEE Communications Society. - 9781479916221
-
Konferensbidrag (refereegranskat)abstract
- The adoption of electrostatic (Coulomb) forces to acquire and maintain the relative configuration in a spacecraft formation is a topic of significant current research interest. Recent technological advances allow the independent charging of each platform enabling the control of their relative position by means of attractive and repulsive forces. This technique could offer high precision, high equivalent specific impulse, and long operational life time. In real space applications, the effectiveness of the electrostatic force should be limited by the plasma shielding effect. The commanded separation among the spacecraft is ruled by the Debye length parameter, which is larger at higher orbital altitudes. MEOs and GEOs are therefore the preferred scenarios for this control technique. Open-loop electrostatically controlled formations should be dynamically unstable, and a feedback control law is needed to stabilize their motion. Indeed, this paper proposes a comparison among possible different strategies to implement this technique. Due to the non-linearity of the governing equations of motion, the problem needs to be suitably formulated to allow the application of some traditional control laws. The classical proportional derivative technique, as well the optimal LQR approach are considered, together with a Lyapunov-based strategy. The more recent State Dependent Riccati Equation (SDRE) control approach, especially interesting for non-linear system, is also applied. The findings of numerical simulations relevant to a small spacecraft cluster in GEO are discussed in depth
|
|
| 14. |
- Felicetti, Leonard, et al.
(författare)
-
Formation flying dynamics analysis by means of a virtual multibody approach
- 2012
-
Ingår i: First IAA Conference on Dynamics and Control of Space Systems 2012. - San Diego, Calif : American Astronautical Society. - 9780877035879 ; , s. 577-596
-
Konferensbidrag (refereegranskat)abstract
- The aim of this paper is to propose the multibody approach as an alternative method for the analysis of the relative motion in a satellite formation and the evaluation of the related control effort. In the suggested implementation the spacecraft are substituted by the joints of a multibody system in which the links, represented as virtual structural elements, reproduce the relative constraints in position and attitude among the platforms. The idea is to consider the commanded, time-varying orientation and length of the links such that the joints will eventually assume the relative geometry which is the formation's target state at a given time. The forces and torques to be provided to the real spacecraft belonging to the formation are related to the reaction torques and forces which are provided at the joints in the corresponding multibody representation. These reactions can be easily computed by available multibody codes, and can be inserted in a standard orbital propagator to compute the dynamical behaviour of a formation and to validate the approach.
|
|
| 15. |
- Felicetti, Leonard, 1982-, et al.
(författare)
-
Image-based attitude maneuvers for space debris tracking
- 2018
-
Ingår i: Aerospace Science and Technology. - : Elsevier. - 1270-9638 .- 1626-3219. ; 76, s. 58-71
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes an image-based control scheme for tracking space debris using onboard optical sensors. The proposed strategy uses an onboard camera for detecting space debris. The camera is rigidly attached to the satellite; therefore specific attitude maneuvers need to be performed during different phases of the mission. First, the spacecraft orients its attitude to point the camera toward a fixed direction in space, and then when debris traces streak across the field of view of the camera, the spacecraft follows and tracks the motion of the debris. Finally, a disengagement maneuver is executed to stop the spacecraft rotation when the debris disappears from the camera field of view. The model and the developed control scheme take into account the typical characteristics of space-qualified cameras, and a Kalman filter is developed to reduce the effects of the camera noise, detect and predict the path of the debris in the image plane, and estimate the angular velocity of the spacecraft. The entire estimation/control scheme is then validated through numerical simulations, using a model of reaction wheels as the main attitude actuation system. The results demonstrate the viability of such maneuvers in a typical space debris surveillance mission scenario.
|
|
| 16. |
- Felicetti, Leonard, et al.
(författare)
-
Modeling the formationkeeping control with multibody codes
- 2012
-
Ingår i: 2012 IEEE Aerospace Conference; Big Sky, MT. - Piscataway, NJ : IEEE Communications Society. - 9781457705564
-
Konferensbidrag (refereegranskat)abstract
- Formation Flying control involves the computation of relative kinematics and dynamics among a number of orbiting platforms. Formations are not the only space application in which several components operate coordinately at the same time. "Multibody" is the scheme usually adopted to model the robotic arms of the space manipulators or large space platforms as the International Space station, and multibody can be also seen as a set of components orbiting together. A number of software codes have been developed during the years to represent and simulate this scheme, taking into account the differential forces acting on each member. This paper proposes to build on this effort to test a different way for evaluating the control of spacecraft formations. The formation spacecraft will be represented by the joints of the multibody. The links, represented as structural element with infinite stiffness, virtually reproduce the relative constraints in position and attitude among the platforms. The idea is to consider the orientation and the length of the links such that the joints (spacecraft) will actually assume the relative geometry which is the desired state at a given time. The forces and torques to be provided to the real spacecraft belonging to the formation are related to the reaction torques and forces which are provided at the joints in the corresponding multibody representation. These reactions can be easily computed by available multibody codes, and the values found can be applied to a standard orbital propagator to compute the dynamical behavior and to validate the approach. The advantage stays with the quick, easy computation of the inverse kinematics, which is routinely performed by multibody software. The solution should be useful to both the cases of keeping an already acquired configuration, like large distributed antennas virtually built by several spacecraft, as well as to the rigid reorientation of a formation, like in some astronomical missions
|
|
| 17. |
- Felicetti, Leonard, et al.
(författare)
-
Nanosatellite missions for in situ low orbital height atmospheric measurements enabled by laser propulsion re-orbiting
- 2010
-
Ingår i: 61st International Astronautical Congress 2010 (IAC 2010). - Paris : International Astronautical Federation. - 9781617823688 ; , s. 9841-9850
-
Konferensbidrag (refereegranskat)abstract
- In situ atmospheric measurements at low orbital heights are necessary to build accurate atmospheric models and in particular to contribute to the development of a global, real time, space weather forecasting service, following the high variability of the atmospheric environment and allowing accurate predictions of LEO object trajectories and maneuvers planning. Missions for real-time in situ atmospheric measurements have been recently proposed, based on nanosatellite swarms. The main limitation in these missions is the effect of atmospheric drag, which dissipates the orbital energy making the nanosatellite re-enter and burn quickly in the Earth atmosphere. Therefore, the operative orbit height must be sufficiently high to guarantee a meaningful orbital lifetime, justifying the launch and sophisticated instrumentation costs. Using a propulsion system, the useful satellite lifetime could be extended and at the same time the operative orbit height could be lowered, to explore more interesting zones. However, conventional propulsion systems, namely chemical and electric propulsion systems, are not compatible with the on board resources constraints imposed by nanosatellites, in terms of mass and power. Innovative propulsion techniques enabling atmospheric measurement missions at low altitudes should be investigated. Among these, laser propulsion offers great weight and power potential savings, obtained separating the propulsion system energy source from the satellite. The energy source for the propulsion system is a laser beam generated remotely, while only a collecting mirrors and ablative material are necessary on the target spacecraft. The mission proposed in this paper is based on the idea that the source of the propulsion energy necessary for the whole nanosatellite swarm can be concentrated in one or more large satellites orbiting at higher altitudes, where the atmospheric drag can be easily compensated. Energy is transferred to the low orbit target nanosatellites by a laser beam, that impinges on the nanosatellite's surfaces, vaporizes a cover slide of ablating material, giving net thrust to the target nanosatellite. The mission is designed taking into account long term orbital perturbations on the target nanosatellite swarm and on the laser source spacecraft. The laser sustained re-orbiting maneuver sequence is optimized, depending on the relative orbital geometry, showing that the laser propulsion system is an enabling technology for low altitude nanosatellite aeronomy missions.
|
|
| 18. |
- Felicetti, Leonard, et al.
(författare)
-
Nanosatellite swarm missions in low Earth orbit using laser propulsion
- 2013
-
Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638 .- 1626-3219. ; 27:1, s. 179-187
-
Tidskriftsartikel (refereegranskat)abstract
- Many missions could benefit from the exploitation of very low height orbits, including Earth observation, atmospheric measurement and space weather research missions. However satellite's lifetime decreases very quickly when the mission requires to orbit into the dense layers of the atmosphere. The mission performance could be enhanced using innovative propulsion techniques, counteracting the effect of atmospheric drag. Among these, laser propulsion potentially offers great weight and power savings, obtained by separating the propulsion system energy source from the propelled satellite. The energy source for the propulsion system is a pulsed laser beam generated remotely, while only collecting mirrors and ablative material are necessary on the target spacecraft. A mission architecture for very low altitude nanosatellite swarms using a space-based pulsed laser propulsion is described. A simplified laser-sustained re-orbiting maneuver sequence is proposed, leading to a straightforward evaluation of the maneuver times, showing that the laser propulsion system is suitable for low altitude nanosatellite missions
|
|
| 19. |
- Felicetti, Leonard, et al.
(författare)
-
Space webs dynamics and configuration control by means of reaction wheels
- 2012
-
Ingår i: AIAA/AAS Astrodynamics Specialist Conference 2012. - Reston, VA : American Institute of Aeronautics and Astronautics, AIAA. - 9781624101823
-
Konferensbidrag (refereegranskat)abstract
- Space webs are large, deployable systems composed by several spacecraft connected by tethers. Their dynamics is commanded by the directional effects of the gravity gradient on the specific configuration selected. The paper investigates webs' attitude dynamics by means of a model including six degrees of freedom for the spacecraft, and a number of elements, able to support tensile stresses and described only by their position, for the tethers. This model, applied to a planar, axial symmetrical configuration, allows for feasible numerical simulations. Specifically, the capability to command web's attitude by means of momentum exchange devices is investigated, and the possibility to transfer the angular momentum from a wheel actuator located in a central platform to the overall system is proofed.
|
|
| 20. |
- Felicetti, Leonard, et al.
(författare)
-
Spacecraft formation for debris surveillance
- 2017
-
Ingår i: IEEE Aerospace Conference Proceedings. - Piscataway, NJ : Institute of Electrical and Electronics Engineers (IEEE). - 9781509016136
-
Konferensbidrag (refereegranskat)abstract
- This paper explores the viability and performance of a new algorithm for in-orbit space debris surveillance, which utilizes a network of distributed optical sensors carried onboard multiple spacecraft flying in formation. The resulting network of spacecraft is able to autonomously detect unknown debris, as well as track the existing ones, estimate their trajectories, and send the estimation results directly to the mission control centers for planning the required collision avoidance maneuvers. The proposed concept includes (a) an estimation algorithm that allows for sharing observations of common debris objects among spacecraft; (b) a coordination algorithm for the re-orientation of an ad hoc team of spacecraft to align their onboard optical sensors towards common targets; and (c) a control algorithm for the detection and tracking of the debris which uses vision-based attitude maneuvers.
|
|
| 21. |
- Felicetti, Leonard, et al.
(författare)
-
Thermosphere density and wind measurements in the equatorial region using a constellation of drag balance nanospacecraft
- 2014
-
Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 54:3, s. 546-553
-
Tidskriftsartikel (refereegranskat)abstract
- A mission for in situ thermosphere density and winds measurement is described, based on nanospacecraft equipped with a drag balance instrument (DBI) and a GPS receiver. The mission is based on nanosatellite clusters deployed in three orbital planes. In this study, clusters of 10 nanospacecraft are considered, leading to a mission based on a total of 30 nanospacecraft. The geometry analyzed is a symmetrical one, including an equatorial orbit and two orbits with the same inclination and opposing ascending nodes. The main idea is that, by combining the accurate information on the satellite inertial position and velocity provided by the GPS receiver and the drag acceleration intensity provided by the DBI, due to the orbits' geometrical configuration, both atmospheric drag and wind can be resolved in a region close to the orbit nodes. Exploiting the Earth oblateness effect, a complete scan of the equatorial regions can be accomplished in the short mission lifetime typical of very low Earth orbit satellites, even in high solar activity peaks, when the expected nanospacecraft lifetime is about 40 days
|
|
| 22. |
- Felicetti, Leonard, et al.
(författare)
-
Three spacecraft formation control by means of electrostatic forces
- 2016
-
Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638 .- 1626-3219. ; 48, s. 261-271
-
Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on electrostatic orbital control in formation flying by using switching strategies for charge distribution. Natural and artificial charging effects are taken into account, and limits in charging technology and in power requirements are also considered. The case of three spacecraft formation, which is intrinsically different and more difficult than the two spacecraft problem often analyzed in literature, has been investigated. A Lyapunov based global control strategy is presented and applied to perform formation acquisition and maintenance maneuvers, producing as output the required overall charge. Then, a selective and optimized charge distribution process among the satellites is discussed for avoiding charge breakdowns to surrounding plasma, for reducing the power requirements and the number of charge switches. The results of numerical simulations show the advantages and drawbacks of the selected control technique
|
|
| 23. |
- Felicetti, Leonard, 1982-, et al.
(författare)
-
Vision-Aided Attitude Control for Space Debris Detection
- 2018
-
Ingår i: Journal of Guidance Control and Dynamics. - : American Institute of Aeronautics and Astronautics. - 0731-5090 .- 1533-3884. ; 41:2, s. 566-574
-
Tidskriftsartikel (refereegranskat)
|
|
| 24. |
- Korsfeldt Larsén, Alexander, et al.
(författare)
-
A computationally efficient model predictive control scheme for space debris rendezvous
- 2019
-
Ingår i: 21st IFAC Symposium on Automatic Control in Aerospace ACA 2019. - : Elsevier. ; , s. 103-110
-
Konferensbidrag (refereegranskat)abstract
- We propose a non-linear model predictive scheme for planning fuel efficient maneuvers of small spacecrafts that shall rendezvous space debris. The paper addresses the specific issues of potential limited on-board computational capabilities and low-thrust actuators in the chasing spacecraft, and solves them by using a novel MatLab-based toolbox for real-time non-linear model predictive control (MPC) called MATMPC. This tool computes the MPC rendezvous maneuvering solution in a numerically efficient way, and this allows to greatly extend the prediction horizon length. This implies that the overall MPC scheme can compute solutions that account for the long time-scales that usually characterize the low-thrust rendezvous maneuvers. The so-developed controller is then tested in a realistic scenario that includes all the near-Earth environmental disturbances. We thus show, through numerical simulations, that this MPC method can successfully be used to perform a fuel-efficient rendezvous maneuver with an uncontrolled object, plus evaluate performance indexes such as mission duration, fuel consumption, and robustness against sensor and process noises.
|
|
| 25. |
- Pagnozzi, Daniele, et al.
(författare)
-
3D minimum reaction control for space manipulators
- 2014
-
Ingår i: 65th International Astronautical Congress 2014. - : International Astronautical Federation. ; , s. 5524-5534
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a novel controller for a generic 3D multibody space system. The control is designed to minimize the dynamic coupling between one of the bodies and the rest of the system, e.g. a spacecraft endowed with a robotic manipulator. Standard control techniques suffer of some limitations. For instance, the Jacobian Transposed (JT) control does not explicitly address the reduction of the reaction forces over the main body. Or else, the so-called "Reaction Null" (RN) technique has a limited workspace due to the strictness of the constraint of zero reactions over the spacecraft. A new closed-loop controller, called Minimum Reaction (MR) control, is designed by combining the RN and JT approaches, so that the dynamic coupling between base platform and manipulator is reduced, while achieving the desired end effector position with great precision. In fact, the reactions on the base are minimized but not constrained to be null as in RN, so that the workspace of the manipulator is extended at its maximum. To this end, the non-linear 3D dynamics of a multibody system is derived in matrix form. Then, a minimum reaction control problem is formulated and solved analytically using a quadratic cost function. The presented solution is applied to a typical mission scenario involving a robotic arm deployment, both in the case of a rigid multibody system and in the case in which a flexible appendage (such as a solar panel) is included. Results are compared with a Jacobian Transposed controller and a Reaction Null controller and discussed
|
|
| 26. |
- Palmerini, Giovanni B., et al.
(författare)
-
Design of debris removal missions performed by robotic graspers
- 2012
-
Ingår i: 63rd International Astronautical Congress 2012. - Paris : International Astronautical Federation. - 9781622769797 ; , s. 6356-6366
-
Konferensbidrag (refereegranskat)abstract
- The well known increase of the orbiting debris, leading to a critical condition in which additional launches could be precluded, calls for mitigation and removal practices. First, and maybe easier to accomplish with respect to other concepts under study, some missions should be probably carried out in a close fiiture to grasp large unused orbiting objects, like upper stages or idle spacecraft that already ended their operational lifetime. The focus on large objects, even if they are a limited subset of orbiting spent bodies, helps in two ways: The reduction of the cross section for possible impacts, and, more remarkably, the reduction of the number and size of additional debris to be generated in a possible collision. As a result, these targets can justify the cost and the complexity of removal missions which, even if almost traditional in the approach and not-too-far from current operational capabilities, still pose significant technical problems. The paper aims to present the operational sequence of a removal mission to be performed by a robotic spacecraft. The issues relevant for the different phases are discussed, with a special focus on the grasping operations, when the robotic arms of the servicing spacecraft, after the determination of the relative kinematic state of the target, should carcfully embraces and precisely catch, in a safe area, the orbiting body. Such an approach should bypass obstacles like solar panels and avoid the break-up of the target, possibly degraded due to its long exposure to space environment. The results of simulations under reasonable, engineering hypothesis for the mission's scenario are presented, with the estimate of torques and forces to be exerted by the robotic arms. The attitude issues for the servicing spacecraft, as well as the vibration behaviour for an accurate end-effector positioning during robotic arms manoeuvres are considered. The confidence in the findings of these numerical studies is strengthened by the know-how gained with the related experimental activities performed during recent years in the labs at Sapienza Universita' di Roma by means of dedicated, small test-beds
|
|
| 27. |
- Pisculli, Andrea, et al.
(författare)
-
A reaction-null/Jacobian transpose control strategy with gravity gradient compensation for on-orbit space manipulators
- 2014
-
Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638 .- 1626-3219. ; 36, s. 30-40
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamics and the control of space manipulators floating in 3D space is analyzed in this paper. A minimum state variable approach for describing the dynamics of a free-floating space manipulator under gravity and gravity gradient forces is presented. A new control strategy involving a combination of Reaction Null and Jacobian Transpose controllers, including also the gravity gradient compensation, is suggested and compared with the Jacobian Transpose control and the conventional Proportional Derivative control. Several numerical examples will be presented and discussed, considering platforms with single and double manipulators, showing the advantages and drawbacks related to these control strategies.
|
|
| 28. |
- Pisculli, Andrea, et al.
(författare)
-
Deployment analysis and control strategies of flexible space manipulators
- 2013
-
Ingår i: Proceedings of the International Astronautical Congress, IAC. - : International Astronautical Federation. - 9781629939094 ; , s. 5732-5747
-
Konferensbidrag (refereegranskat)abstract
- The dynamics and the control of articulated structures for an in-orbit manipulation is a profitable field of research due to worldwide development. The dynamics and the control of such systems is a challenging task, since the equations that govern their motion are highly nonlinear and the control strategies need to take the limited resources carried on board of the common space systems into account. They refer for instance to limited energy power, limited computational power and limited control power of the actuators; furthermore the base platforms of these robotic systems are generally floating in space or subjected to gravity gradient and other environmental torques and forces. For these reasons an investigation on the deploying strategies for orbiting space manipulators is necessary in order to find the best solutions. In this paper three different control strategies are analyzed: the Reaction Null control, the Jacobian Transpose control and the conventional Proportional Derivative control that are compared in terms of power consumption and of the relevant control efforts. The analysis involves both single and double space manipulator systems. The effects of the elasticity of the motor shafts on the behaviour of the deploying manoeuver are also analysed. Numerical simulations, obtained by a space optimized multibody code, are used for demonstrating the suitability and the proficiency of this kind of control strategies
|
|
| 29. |
- Pomares, Jorge, et al.
(författare)
-
Concurrent Image-based Visual Servoing with Adaptive Zooming for Non-cooperative Rendezvous Maneuvers
- 2018
-
Ingår i: Advances in Space Research. - : Elsevier. - 0273-1177 .- 1879-1948. ; 61:3, s. 862-878
-
Tidskriftsartikel (refereegranskat)abstract
- An image-based servo controller for the guidance of a spacecraft during non-cooperative rendezvous is presented in this paper. The controller directly utilizes the visual features from image frames of a target spacecraft for computing both attitude and orbital maneuvers concurrently. The utilization of adaptive optics, such as zooming cameras, is also addressed through developing an invariant-image servo controller. The controller allows for performing rendezvous maneuvers independently from the adjustments of the camera focal length, improving the performance and versatility of maneuvers. The stability of the proposed control scheme is proven analytically in the invariant space, and its viability is explored through numerical simulations.
|
|
| 30. |
- Pomares, Jorge, et al.
(författare)
-
Spacecraft visual servoing with adaptive zooming for non-cooperative rendezvous
- 2018
-
Ingår i: 2018 IEEE Aerospace Conference. - : IEEE Computer Society. - 9781538620144
-
Konferensbidrag (refereegranskat)abstract
- The utilization of zooming cameras during a non-cooperative rendezvous in space is investigated in this paper. An image-based controller, utilizing visual servoing techniques usually applied to ground-based robotic systems, is designed for the particular problem of far-to-close approach of a spacecraft to a non-cooperative object. The controller directly utilizes the visual features from image frames of the noncooperative target for computing both attitude and orbital maneuvers concurrently. The additional feature derived from the utilization of the zooming camera gives a greater versatility to the maneuvers if compared with the classic fixed optics approaches. The stability of the proposed controller is proven analytically in the invariant space, and its viability is explored through the application to a realistic space debris removal scenario
|
|
| 31. |
- Santoni, Fabio, et al.
(författare)
-
Attitude dynamics and control of drag-balance CubeSats
- 2013
-
Ingår i: Journal of Guidance Control and Dynamics. - : American Institute of Aeronautics and Astronautics (AIAA). - 0731-5090 .- 1533-3884. ; 36:6, s. 1834-1839
-
Tidskriftsartikel (refereegranskat)abstract
- The article examines the system stability, obtaining upper bounds for the mass unbalance to verify the applicability of magnetic control laws valid for rigid bodies to the drag-balance CubeSat two-body system. The rod is connected to the satellite body by two flexural springs. The spin axis is orthogonal to the rod, exposing the plates to the incoming atmosphere flux at the spin rate and generating a relative displacement between the DBI and the satellite. The spin frequency component of this displacement is therefore related to the atmospheric drag force and can be evaluated by measuring the displacement itself and isolating the spin frequency content. Single-, double-, and triple-unit CubeSat implementations of the DBI concept are possible. The drag-balance CubeSat attitude control system must provide for attitude acquisition, spin axis orbit normal pointing, spin rate estimation, and regulation.
|
|
